Here is a full list of all lockbox keycodes. SPOILER ALERT!!!
Spawn room

KEYCODE: 5721
This keycode is found on your laptop (ESC) in the folder “Don’t forget”.
Cracked Glass Door

KEYCODE: 7315
This keycode is found by refusing to give a cig to the guy in the meeting room.
Fun Dungeon

KEYCODE: 6669
This keycode is found giving a cig to the employee that’s on the boat outside the fun dungeon.
Evidence Room

KEYCODE: 8263
This keycode is found in a sticky note on a nearby laptop.
Below Warper Item

KEYCODE: 6734
This keycode is found talking to the NPC on the couch near the lockbox with music turned off.

Chemico

KEYCODE: 9225
This keycode is found on the whiteboard in the room 604 that you can only acess after completing all tags.